[jira] [Created] (CASSANDRA-7994) Commit logs on the fly compression

["Oleg Anastasyev (JIRA)" <ji...@apache.org>]

Oleg Anastasyev created CASSANDRA-7994:
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             Summary: Commit logs on the fly compression 
                 Key: CASSANDRA-7994
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7994
             Project: Cassandra
          Issue Type: New Feature
            Reporter: Oleg Anastasyev


This patch employs lz4 algo to comress commit logs. This could be useful to conserve disk space either archiving commit logs  for a long time or for conserviing iops for use cases with often and large mutations updating the same record.

The compression is performed on blocks of 64k, for better cross mutation compression. CRC is computed on each 64k block, unlike original code computing it on each individual mutation.

On one of our real production cluster this saved 2/3 of the space consumed by commit logs. The replay is 20-30% slower for the same number of mutations.

While doing this, also refactored commit log reading code to CommitLogReader class, which i believe makes code cleaner.



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